I never really thought about it before but I guess a salaried position goes both ways. if your not being paid hourly then if your meeting the requirements of the job can you not work on other things "during work hours"
Whether you make both companies aware is a personal choice. I only worked with companies who had absolutely nothing to do with one-another, ensuring they were in different industries. I also always made sure that any contracts I signed were vetted and that I was in the clear.
For me personally, I always made it clear that my time belonged to me and that I had other things going on. I set realistic expectations based on my compensation and met those expectations. It was never a problem for me. That would sometimes mean that I was working 20 hour days if there was a crunch or emergency at both places, but that was also generally followed by ample time off.
I never really thought about it before but I guess a salaried position goes both ways. if your not being paid hourly then if your meeting the requirements of the job can you not work on other things "during work hours"